Income Taxes - Provision for Income Taxes Attributable to Income from Continuing Operations (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Tax at U.S. federal statutory rates									$ 16,766	$ 26,012	$ 23,452
State taxes (net of federal benefit)									4,035	2,945	2,643
Business meals and entertainment — non-deductible									915	820	784
Reserves for uncertain tax positions									(1,124)	(35)	(87)
Share-based compensation									(3,260)	(3,837)
Impact of the Tax Cuts and Jobs Act of 2017										(2,487)
Non-deductible expenses									785	236	22
Other, net									150	(366)	(415)
Provision for income taxes from continuing operations	$ (1,424)	$ 3,297	$ 3,238	$ 13,156	$ (3,368)	$ 6,172	$ 4,343	$ 16,141	$ 18,267	$ 23,288	$ 26,399
Effective income tax rate									22.90%	31.30%	39.40%